Self-crimping yarn

Abstract

Polyester polymer is extruded through converging capillaries at different speeds to merge and form a combined stream. The stream is cooled to form a filament, which is withdrawn at a high speed. A plurality of such filaments are combined into yarn which self-crimps upon heating. In some embodiments, the yarn has a variable denier.

What is claimed is: 
     
       1. An as-spun self-crimping yarn comprising a plurality of polyester continuous filaments, (a) said filaments having non-round cross-sectional areas which vary substantially regularly along the lengths of said filaments from regions of large cross-sectional area to regions of small cross-sectional area, said variation in cross-sectional area being more than ±10% about a mean value,   (b) said regions of large and small cross-sectional area being out of phase from filament to filament to thereby form said self-crimping yarn.   
     
     
       2. The yarn defined in claim 1, wherein said variation in cross-sectional area is at least ±30% about said mean value. 
     
     
       3. The yarn defined in either of claims 1 or 2, wherein said regions of large cross-sectional area have substantially higher shrinkage than said regions of small cross-sectional area whereby said filaments have shrinkage profiles in the form of shrinkage peaks in said regions of large cross-sectional area and shrinkage valleys in said regions of small cross-sectional area. 
     
     
       4. The yarn defined in claim 3, wherein said shrinkage profiles are in the form of an average of at least two broad shrinkage peaks per 5 meters along the length of each of said filaments, said peaks and valleys being out of phase from filament to filament. 
     
     
       5. The yarn defined in claim 4, wherein at least one of said filaments has an average denier less than 5. 
     
     
       6. The yarn defined in claim 3 wherein each of said polyester continuous filaments has a shrinkage of less than 30%. 
     
     
       7. The yarn defined in claim 6 wherein each of said polyester continuous filaments has a shrinkage of less than 10%.